Smart objects are devices whose primary function is augmented with intelligent behavior and communication capabilities. Many everyday devices can be utilized more effectively, or in new ways, by embedding some intelligence in them. This trend is already apparent in some lighting products for the home and office market. Examples are daylight sensing or presence detection. These are simple examples of combining several objects with communication capabilities and making them more than the sum of their parts. As more and more devices will be equipped with micro processors and communication capabilities, more complex inter-device behaviors will emerge.
A very likely candidate for a new communication backbone is the Internet, enabled through Ethernet or other LAN networking. Ethernet has the major advantage that it is everywhere, and due to the massive volumes involved, equipping a device with Ethernet communication means can be easily done at low costs. Ethernet was developed around 1975 by Xerox and has seen multiple upgrades and improvements since. Ever since Ethernet transitioned to the well known 8P8C/10BASE-T (or RJ45) connector and cabling, it has enjoyed full backward compatibility with older devices. Due to the enormous amount of devices compatible with this technology, this form of Ethernet is supposed to survive for many more years.
A very interesting recent addition to Ethernet is the capability to also deliver DC power over the Ethernet cables, while remaining fully compatible with equipment that does not make use of this. Power-over-Ethernet (PoE) is an IEEE standard (IEEE 802.3.af and IEEE 802.3.at) which allows supplying DC low voltage over low cost Cat5/6 cables. The current IEEE 802.3at standard allows for a delivered power of 25.5 W (at 42.5V-57V) to a powered device (PD). As the industry is more and more discussing DC distribution as an efficient future alternative for the well known AC mains also supplying power to lighting devices via PoE may get used widely.
Power efficiency in PoE systems is becoming ever more important. There are many factors that determine power efficiency in a PoE system. Among others, PoE system performance depends on the overall system installation performance between the power sourcing equipment (PSE), e.g., PoE switches, and the PD's, e.g., luminaires. A badly installed system (e.g., too long cables, bad cables/connections, wrong cable type, etc.) can have a major impact on power efficiency of the total system, including maintenance.
However, the length and quality of cables are often overlooked. As an example, the installer may simply use standard length cables that are too long (leading to energy losses) instead of cutting them at the right length or a standard length cable of appropriate length. As a further example, the installer may use lower quality cables than required (e.g. by the customer). During (and after) installation it would therefore be worthwhile to get feedback related to this aspect.
The US 2008/172564 A1 discloses a system and method for controlling delivery of power to a powered device in a Power over Ethernet Broad Reach (PoE-BR) application. Cabling power loss in the PoE-BR application is related to the resistance of the cable itself. A PHY can be designed to measure electrical characteristics (e.g., insertion loss, cross talk, length, etc.) of the Ethernet cable to enable determination of the cable resistance. The determined resistance in a broad reach cable can be used in increasing a power budget allocated to a power source equipment (PSE) port. Thereby, dynamic power location in dependence on the cable resistance can be achieved to provide the required power budget at each port.
Additionally, the EP 1 928 121 A2 discloses a similar system which can be used for diagnostic of cabling infrastructure so as to determine a capability to handle a specific application.
Moreover, the US 2008/229120 A1 discloses another similar system where the cable resistance is determined to determine whether the cable has exceeded specific operating thresholds (e.g. cable heating). Furthermore, a diagnostic capability is provided to determine deterioration of a cable.
In addition, the EP 1 936 861 A1 discloses another similar system where a power budget allocated to a PSE port is adjusted based on a determined type of Ethernet cable. Furthermore, a diagnostic tool is provided, which can be used to identify the Ethernet cable which is connected to a PSE port.
Furthermore, the EP 2 498 444 A1 discloses a still further similar system where link diagnostic capability information (e.g. cable type) is exchanged to enable a pair of powered devices to coordinate and leverage link-related information generated by their link diagnostics.
Additionally, the EP 2 439 496 A1 discloses a system for detecting loss in a network by analyzing received average measured voltage and current values from points of consumption by using calculated conductivity parameters to detect any deviations of measured current values from calculated current values with respect to a given point of consumption or point of supply.
Finally, the US 2008/170509 A1 discloses a PoE system capable of determining a cable type based on measured electrical characteristics. The determined cable type can be used in diagnosis of cabling infrastructure or dynamic configuration.